I managed to get my hands on a test sample D4 2 days ago and I decided to have a ISO test round-up against it's older brother - the Nikon D3 ( that I own ). I didn't have a D3s to put it up against, however, results turned out to be quite surprinsing.

PS. please bare in mind the article is written in 2 languages ( Romanian and English ) - and also technically speaking there was a bit of an AF align issue with the testing lens on my D3, which I noticed home so there will be a bit of a sharpness difference due to this fact - however the main goal here is to test iso/noise ratio.